Wireless local area network (LAN) system

ABSTRACT

A situation is circumvented where wireless communication becomes impossible in a wireless LAN system under the influence of a blocking object, noise caused by an electromagnetic wave, or the like. A wireless LAN system comprises: a relay which can communicate with an external system; a master which can communicate with the relay; and a plurality of slaves which can wirelessly communicate with the master, the plurality of slaves including a first group and a second group, the first group comprising an alternative slave having a function of transmitting, when a portion of the slaves cannot receive a synchronization signal from the master, an information signal received from the master to the portion of slaves, and the second group comprising non-alternative slaves and not having the function of transmitting the information signal to the portion of slaves.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of copending U.S. patent applicationSer. No. 12/599,104, filed Nov. 25, 2009, entitled “Wireless Local AreaNetwork (LAN) System”, which is herein incorporated by reference, whichis a National Stage application of International ApplicationPCT/JP2008/057532, filed Apr. 17, 2008. This application claims priorityunder 35 U.S.C. §120 of U.S. patent application Ser. No. 12/599,104,filed Nov. 25, 2009 and of International Application PCT/JP2008/057532,filed Apr. 17, 2008. This application further claims priority under 35U.S.C. §119 of Japanese Application 2007-123906, filed May 8, 2007.

FIELD OF THE INVENTION

The present invention generally relates to a wireless local area network(LAN) system. More specifically, the present invention relates to a LANsystem in a relatively small space such as a home or office.

BACKGROUND ART

In recent years, IEEE 802.11a/g/b-based wireless LANs have become commonfor home use. Higher speed wireless standards are also underdevelopment. In the industry, there are trends to place wireless LANs ashome network infrastructure by the distribution of AV streams using ahigh-speed wireless LAN, a home security sensor (glass breakagedetection) using the easiness of wireless installation, and the like.

Meanwhile, due to characteristics of radio waves, wireless LANs aresusceptible to blocking objects, noise caused by electromagnetic waves,and the like. Particularly, millimeter waves, UWB, etc., for high-speedwireless LANs are susceptible to obstacles and the like. In order tospread high-speed wireless LANs as home network infrastructure, there isa need to take measures against such interference.

However, wireless LANs are premised on an ad-hoc connection (which isnot continuous communication but a dynamic network connection). Thus,wireless disconnection is not recognized as an abnormal condition. TheIEEE 802.15.3 standard and the like do not even consider a mechanism fortreating wireless disconnection as an abnormal condition. Also, there isno mechanism for notifying communication disconnection in a wirelessnetwork layer. Particularly, in the case of a network where a wiredportion is tunneled (an IP packet or Ethernet frame is encapsulated), adevice on the Ethernet side considers wireless disconnection as anunexplained communication failure.

The development of the high-speed wireless LAN is still at anexperimental stage towards the practical use. In current measures,circumventing measures from the viewpoint of devising strategies forprevention of radio interference, such as “sending radio waves from alocation with a clear view using a waveguide” or “appropriatelyadjusting an output” is mainstream.

As a conventional technique, Japanese Unexamined Patent Publication(Kokai) No. 2004-282758 discloses a method in which, in a wirelessnetwork which is controlled by a single controller, when the controllerbreaks down (or stops) the controller is switched to an alternativecontroller and network control is performed using the alternativecontroller, whereby the wireless network is maintained. However, thismethod is not to circumvent a situation where wireless communicationbecomes difficult under the influence of a blocking object, noise causedby an electromagnetic wave, or the like.

SUMMARY

It is an object of the present invention to automatically maintain acommunication service when radio interference occurs in a wireless LANsystem.

It is another object of the present invention to circumvent a situationwhere wireless communication becomes impossible in a wireless LAN systemunder the influence of a blocking object, noise caused by anelectromagnetic wave, or the like. Note that the expression “wirelesscommunication becomes impossible” as used herein involves not only thecase where communication cannot be performed at all but also the case inwhich communication cannot be performed stably (e.g., the case in whichcommunication frequently or intermittently is lost).

According to one embodiment of the present invention, there is provideda wireless LAN system comprising: a relay which can communicate with anexternal system; a master which can communicate with the relay; and aplurality of slaves which can wirelessly communicate with the master,the plurality of slaves including a first group and a second group, thefirst group comprising an alternative slave having a function oftransmitting, when a portion of the slaves cannot receive asynchronization signal from the master, an information signal receivedfrom the master to the portion of slaves, and the second group includingnon-alternative slaves not having the function of transmitting theinformation signal to the portion of slaves.

According to another embodiment of the present invention, there isprovided a wireless communication method between a master and aplurality of slaves which are included in a wireless LAN system,comprising the steps of: transmitting a first synchronization signal tothe plurality of slaves from the master; transmitting a first receivedsignal to the master from a slave having received the firstsynchronization signal; sending a second synchronization signal from aspecific slave among the plurality of slaves to other slaves;transmitting a second received signal to the specific slave from slaveshaving received the second synchronization signals; transmitting aninformation signal to the specific slave from the master; andtransmitting the information signal from the specific slave to a slavenot having sent a first received signal among the slaves having receivedthe second synchronization signals.

According to an embodiment of the present invention, even whencommunication becomes impossible between a master and a portion ofslaves in a wireless LAN system due to wireless communication failurecaused by an obstacle, noise, or the like, an alternative communicationroute between the master and the portion of slaves can be automaticallysecured.

According to an embodiment of the present invention, when communicationbecomes impossible between a master and a portion of slaves in awireless LAN system due to wireless communication failure caused by anobstacle, noise, or the like, a specific slave among slavesautomatically substitutes for (relays) the master, whereby thecommunication between the master and the portion of slaves can bemaintained.

According to an embodiment of the present invention, when wirelesscommunication failure caused by an obstacle, noise, or the like in awireless LAN system is removed, the communication route canautomatically revert to the one used before occurrence of the failure.

According to and embodiment of the present invention, regardless ofoccurrence of wireless communication failure caused by an obstacle,noise, or the like in a wireless LAN system, a communication (service)between a master and slaves can be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a basic configuration of a LAN packetcommunication system using a normal PICONET, according to the presentinvention;

FIG. 2 is a diagram showing a system configuration in the presentinvention;

FIG. 3 is a diagram showing a system configuration (before occurrence offailure) in the present invention;

FIG. 4 is a diagram showing a system configuration (immediately afteroccurrence of failure) in the present invention;

FIG. 5 is a diagram showing a system configuration (a state showingsecuring of an alternative route after occurrence of failure) in thepresent invention;

FIG. 6 is a diagram showing a switching table and a connection tablewhich are included in a PNC;

FIG. 7 is a diagram showing a table for the case in which a DEV-B (#5)in FIG. 2 is registered as IP#5;

FIG. 8 is a diagram showing a table for the case in which a DEV-B (#4)in FIG. 2 is registered as IP#4;

FIG. 9 is a diagram showing a state in which, after #4 in FIG. 8 isrecognized, DEVs-B with #3 and #6 are further connected;

FIG. 10 is a diagram showing a state in which connections between theDEVs-B (#3 and #4) and the PNC are disconnected;

FIG. 11 is a diagram showing a state in which a connection between theDEV-B (#3) and the PNC is secured by an alternative route via a DEV-A(#1); and

FIG. 12 is a diagram showing a state in which the interference isremoved and the original connection between the DEV-B (#3) and the PNCis recovered.

DETAILED DESCRIPTION

The present invention will be described below with reference to thedrawings. The following description is premised on the use of PICONETbased on the IEEE 802.15.3 standard. However, the present invention isnot limited to this premise and other standards, methods, or the like,can of course be used.

In one embodiment of the present invention, a system for transmittingand receiving LAN packets in an IEEE 802.15.3 PICONET is assumed.PICONET refers to a wireless communication subnet defined by IEEE802.15.3. In the present embodiment, the following contents (A and B)are disclosed. Note that a ChildPICONET which appears below refers tothe minimum unit of a network defined by IEEE 802.15.3.

A. System for dynamically securing another route using a ChildPICONET,when a failure (wireless disconnection) occurs

(a-1) System configuration for securing another route during failure(wireless disconnection)

(a-2) Method for detecting occurrence of failure (wirelessdisconnection), by each device in the system

(a-3) Method for selecting another route

(a-4) Method for detecting recovery from failure and reverting to theoriginal route

B. Method for recognizing, in a wireless layer, occurrence of failure ina wireless portion between specific devices and alerting notifiedfailure

FIG. 1 shows a basic configuration of a LAN packet communication systemusing a PICONET, according to the present invention. In thisconfiguration, a PNC (PICONET coordinator) 10 for controlling a PICONETis wirelessly connected to a plurality of DEVs (DEVices) 20 and a LANpacket is tunneled (or protocol-converted). The PNC 10 is connected toan external system via a relay (not shown). In optical communication(FTTH), a relay includes a converter for converting light into anelectrical signal (millimeter wave or the like). A line 30 between thePNC 10 and each DEV 20 means the presence of a wireless communicationroute. The meaning of the lines 30 is also the same in other drawings.IP#1 to IP#4 represent LAN devices (PCs, various household electricalappliances, or the like) assigned to the respective DEVs. At the sametime, IP#n also represents an Ethernet MAC address or an IP address ofan IP packet, which corresponds to each device. The meaning of IP#n isalso the same in other drawings.

IEEE 802.15.3 defines that devices in a PICONET can mutuallycommunicate. In communication that provides an Internet connection to ahome, communication between DEVs also uses a route of DEV→PNC→DEV forthe following reasons:

(a) a PNC is only one gateway to the Internet; and

(b) the DEVs are not always installed in communicable areas.

Although the connection to the PICONET is ad hoc, a route of a LANpacket is configured by a combination of DEVs and the PNC. In order toexpand a wireless coverage, IEEE 802.15.3 also defines that a childPICONET can be used.

A. System for dynamically securing another route when a failure(wireless disconnection) occurs

(a-1) System configuration for securing another route during failure(wireless disconnection)

FIG. 2 shows a system configuration in the present invention forsecuring another route during failure (wireless disconnection). There isone PNC 100. DEVs are of two types: DEV-A and DEV-B. DEV-As 110 have thefunction of becoming a PNC of a child PICONET. DEVs-B 120 do not havethe function of becoming a PNC.

Referring to FIGS. 3 to 5, a process flow performed during failure(wireless disconnection) is shown below.

(1) In FIG. 3, in one PICONET which is normally managed by a PNC 100,the PNC 100, DEVs-A, and DEVs-B perform wireless communication.Specifically, LAN packet communication is performed with LAN devices(IP#n). In FIG. 3, for example, the PNC 100 communicates with IP#3 of aDEV-B 122.

(2) In FIG. 4, when an obstacle 200 or the like is placed, some DEVs-Bbecome unable to communicate with the PNC 100. In FIG. 4, two DEVs-B,i.e., a DEV-B 122 (IP#3) and a DEV-B 124 (IP#4), cannot communicate withthe PNC 100.

(3) In FIG. 5, a DEV-A 112 which has detected a failure (wirelessdisconnection) operates as an alternative PNC and creates a childPICONET. In FIG. 5, the DEV-B 122 (IP#3) and the DEV-B 124 (IP#4) whichhave become unable to communicate with the PNC 100 switch theirconnections to the DEV-A 112 (PNC). LAN packets are transmitted throughan alternative route of PNC 100-DEV-A 112-DEV-B 122/124.

(4) When the failure is removed, the route reverts to the original oneshown in FIG. 3.

The operation of the system in the present invention exemplified inFIGS. 2 to 5 has the following two features.

(1) In a conventional method for selecting an alternative route for anetwork failure, complex routing information exchange based on a routingprotocol is performed. In the present invention, however, only bymulticasting by a device a packet for notifying other devices of itspresence, switching to an alternative route is performed. The method ofthe present invention is different from a conventional one in which theload of routing information exchange is heavy and a route request ismade during failure, and thus, fast switching to an alternative route isperformed.

(2) In the present invention, handling devices that require a staticconnection in distinction from devices (ad hoc) that do not require astatic connection can prevent an increase in system load caused byactivation of an unnecessary alternative route.

(a-2) Method for detecting occurrence of failure (wirelessdisconnection), by each device in the system

The PNC periodically sends a beacon (synchronization signal) to informeach DEV of its presence. Sending of a beacon is performed based on IEEE802.15.3. DEVs-A periodically transmit a “static connection info”packet. The PNC has (a) switching table and (b) connection table shownin FIG. 6, in order to manage a connection relationship with each DEV.In (b) connection table in FIGS. 6, #1 and #2 are entered as DEVs(DEVs-A) of type A. The term “static” in (b) connection table refers toa static connection. (#2) and (#1) shown next to the terms “static”respectively indicate that the DEV-A (#1) can see (communicate with) theDEV-A (#2) and vice versa. If the PNC does not receive a “staticconnection info” packet for a certain period of time, the PNC determinesthat the DEVs-A cannot be seen.

Among DEVs of type B, a DEV-B that requires a static connectionperiodically multicasts a “static connection info” packet. The “staticconnection info” packet is the same as the one used to verify thepresence of a DEV-A. FIG. 7 shows a table for the case in which a DEV-B(#5) in FIG. 2 is registered as IP#5. (b) connection table in FIG. 7shows that the DEV-B with #5 is static and can be connected to theDEVs-A with #1 and #2.

A DEV-B that does not require a static connection, i.e., a DEV-B usingan ad-hoc connection, does not multicast a “static connection info”packet. This DEV-B operates as defined in IEEE 802.15.3. FIG. 8 shows atable for the case in which a DEV-B (#4) in FIG. 2 is registered asIP#4. In (b) connection table in FIG. 8, information that the DEV-B with#4 is ad hoc is entered. As such, by using a connection table, even whenboth static and ad-hoc devices are present, the devices can beappropriately managed.

(a-3) Method for selecting another route

A selection of another route is performed in the manner shown belowusing switching tables managed by PMC/DEV-A.

(1) In FIG. 9, in a normal state, based on (b) switching table of thePNC 100, a LAN packet is encapsulated by a protocol of a wirelessportion to perform tunneling. FIG. 9 shows a state in which, after #4 inFIG. 8 is recognized, DEVs-B with #3 and #6 are further connected.

(2) In FIGS. 10 and 11, it is assumed that connections between theDEVs-B (#3 and #4) and the PNC 100 are disconnected, for example.

2-1) The DEV-B 124 with #4 that does not require a static connectioncloses its connection as defined in IEEE 802.15.3.

2-2) The DEV-B 122 with #3 that requires a static connection isconnected to the DEV-A 112 which is an alternative PICONET (childPICONET managed by #1).

2-3) The DEV-A (#1) 112 registers IP#3 in (a) switching table includedin #1.

2-4) The DEV-A (#1) 112 notifies the PNC (#0) 100 that #3 is connectedto the DEV-A (#1) 112 as an alterative path (a process of thisnotification by #0 is asynchronous).

2-5) The PNC 100 having detected the disconnection from #3 and #4deletes information on #3 and #4 from (b) switching table (FIG. 10).

2-6) When a LAN packet destined for #3 arrives, the PNC 100 broadcaststhe LAN packet throughout the PICONET.

2-7) The DEV-A (#1) receives the LAN packet and transmits the LAN packetto #3 registered in the switching table of #1.

2-8) The DEV-B (#3) send/receives the LAN packet through an alternativeroute of #0<->#1<->#3.

(3) When a process by #1 in the above 2-4) ends, information indicatingthat data to #3 is transmitted via #1 (DEV#1) is registered in (b)switching table (FIG. 11) of the PNC (#0) 100. After this, when a LANpacket destined for #3 arrives, the PNC 100 unicasts the LAN packet tothe DEV-A (#1).

(a-4) Method for detecting recovery from failure and reverting to theoriginal route

In FIG. 12, the DEV-B (#3) 122 using the alternative route monitorsresumption of a beacon from the PNC 100. When a beacon is resumed byremoval of the obstacle, for example, the connection of the DEV-B (#3)122 to the PNC 100 reverts. The contents of the switching tables of thePNC 100 and the DEV-A (π1) 112 are reset to normal and transmission andreception of a LAN packet using the original route are performed.

For a method for recognizing, in a wireless layer, occurrence of failurein a wireless portion and alerting notified failure, first, whether aconnection request by each DEV is static or ad hoc is managed using aconnection table. When a situation different from a normal one occurs,the PNC or a DEV provides a notification. The notification is performedby an email, sound, phone call, or the like. Information that anotification is being provided is entered in and managed by theconnection table.

A PNC of the present invention operates as a PC based dedicated device,for example, by SW which operates thereon. A DEV-A of the presentinvention is installed in a room, for example, so as to be seen from aplurality of DEVs-B and the PNC (in a wirelessly communicable manner). ADEV-A is provided as a box-type device having an Eth/millimeter-waveinterface, for example. Such a device can incorporate embedded software(SW) for implementing a method of the present invention. The device isoperated based on some kind of embedded OS and functions as a driver foroperating hardware (HW) of the Eth/millimeter-wave interface included inthe device.

When a DEV-B of the present invention is a terminal personal computer(PC), for example, the DEV-B is operated by software which is suppliedwith a millimeter-wave wireless LAN card. Alternatively, when the DEV-Bis an external device (when the DEV-B is a LAN-compatible securitydevice or household electrical appliance which cannot expand a card asin a PC), the DEV-B is operated by embedded SW which operates in abox-type device, as with the DEV-A.

The present invention has been described with reference to the drawings.However, the present invention is not limited to the above-describedembodiment. It will be obvious to those skilled in the art thatmodifications may be made to the embodiment without departing from thespirit and scope of the present invention.

What is claimed is:
 1. A wireless communication method for performingwireless communication between a master and a plurality of slaves whichare included in a wireless local area network (LAN) system, the masterperforming the steps of: establishing a respective direct wirelessconnection between said master and each of said plurality of slaveswherein communications between said master and each respective slave ofsaid plurality of slaves are transmitted via respective direct wirelesstransmission between said master and the respective slave withoutre-transmission through another device; periodically transmitting amaster synchronization signal directly from said master to saidplurality of slaves, said master synchronization signal beingtransmitted via respective direct wireless transmission from said masterto each slave of said plurality of slaves without re-transmissionthrough another device, said master synchronization signal requiring arespective master synchronization response signal from each of saidplurality of slaves; responsive to periodically transmitting a mastersynchronization signal, periodically receiving a respective mastersynchronization response signal from each of said plurality of slaveshaving received the master synchronization signal, each respectivemaster synchronization response signal being received via directwireless transmission from the respective slave to said master withoutre-transmission through another device; detecting that no correspondingmaster synchronization response signal has been received from a firstslave of said plurality of slaves responsive to an instance ofperiodically transmitting said master synchronization signal; responsiveto detecting that no corresponding master synchronization responsesignal has been received from a first slave of said plurality of slavesresponsive to an instance of periodically transmitting said mastersynchronization signal, transmitting an instruction signal from saidmaster to a specific slave among the plurality of slaves to urge thespecific slave to send a slave synchronization signal, said specificslave being other than said first slave; responsive to transmitting aninstruction signal from said master to the specific slave, receivingfrom the specific slave an acknowledgment signal indicating that thefirst slave has received the slave synchronization signal; thereafterreceiving in said master an information packet addressed to said firstslave; and responsive to receiving the information packet, transmittingto the specific slave the information packet for forwarding to the firstslave.
 2. The wireless communication method of claim 1, wherein wirelesscommunications among said master and said plurality of slaves areaaccording to an IEEE 802.15.3 PICONET protocol.
 3. The wirelesscommunication method of claim 1, further comprising resumingtransmitting information packets directly from said master to said firstslave responsive to receiving an indication from the first slave,responsive to an instance of said master synchronization signal, thatthe first slave is again capable of receiving signals directly from themaster.
 4. The wireless communication method of claim 1, wherein themaster has a first table and the first table includes a list ofcommunicable slaves.
 5. The wireless communication method of claim 4,wherein the specific slave has a second table and the second tableincludes a list of communicable slaves to which the specific slave iscapable of forwarding communications received from the master.
 6. Thewireless communication method of claim 1, wherein the first slave isunable to respond to the master synchronization signal due to thepresence of an obstacle between the master and the first slave.
 7. Amaster wireless transceiver station for supporting a wireless local areanetwork (LAN) system, comprising: an external network interfaceproviding a gateway to the Internet; a wireless transceiver fortransmitting and receiving wireless communications over a limited rangeusing a pre-defined wireless communications protocol to a plurality ofslave devices within said limited range of said wireless transceiver; acoordinator mechanism which establishes a respective direct wirelessconnection between said master wireless transceiver station and each ofsaid plurality of slave devices wherein communications between saidmaster wireless transceiver station and each respective slave device ofsaid plurality of slave devices are transmitted via respective directwireless transmission between said master wireless transceiver stationand the respective slave device without re-transmission through anotherdevice; wherein said coordinator mechanism periodically transmits amaster synchronization signal using said wireless transceiver directlyto said plurality of slave devices, said master synchronization signalbeing transmitted via respective direct wireless transmission from saidmaster wireless transceiver station to each slave device of saidplurality of slave devices without re-transmission through anotherdevice, said master synchronization signal requiring a respective mastersynchronization response signal from each of said plurality of slavedevices; wherein said coordinator mechanism monitors received responsesto said master synchronization signal from said plurality of slavedevices and detects a failure of a first slave device of said pluralityof slave devices to respond to an instance of said periodicallytransmitting said master synchronization signal; wherein saidcoordinator mechanism, responsive to detecting a failure of said firstslave device to respond to an instance of said periodically transmittingsaid master synchronization signal, transmits an instruction signalusing said wireless transceiver to a specific slave among the pluralityof slaves to urge the specific slave to send a slave synchronizationsignal, said specific slave being different from said first slave;wherein said coordinator mechanism, responsive to receiving from thespecific slave an acknowledgment signal indicating that the first slavehas received the slave synchronization signal transmitted by thespecific slave responsive to the instruction signal, thereaftertransmits using said wireless transceiver any information packetsreceived via said external network interface and addressed to said firstslave to the specific slave for forwarding to the first slave.
 8. Themaster wireless transceiver station of claim 7, wherein predefinedwireless communications protocol is an IEEE 802.15.3 PICONET protocol.9. The master wireless transceiver station of claim 7, wherein saidcoordination mechanism resumes transmitting information packets directlyto said first slave device responsive to receiving an indication fromthe first slave that the first slave is again capable of receivingsignals directly from the master wireless transceiver station, theindication being received responsive to an instance of said mastersynchronization signal.
 10. The master wireless transceiver station ofclaim 7, further comprising a table which includes a list ofcommunicable slave devices.
 11. A first slave wireless transceiverdevice for communication within a wireless local area network (LAN)system having a plurality of slave wireless transceiver devices,comprising: a wireless transceiver for transmitting and receivingwireless communications over a limited range using a pre-definedwireless communications protocol to a master wireless transceiver deviceand at least one other slave wireless transceiver device of saidplurality of slave wireless transceiver devices within said limitedrange of said wireless transceiver, the master device providing agateway to the Internet; a coordinator mechanism which establishes arespective direct wireless connection with said master wirelesstransceiver station, wherein communications between said master wirelesstransceiver station and each respective slave wireless transceiverdevice of said plurality of slave wireless transceiver devices aretransmitted via respective direct wireless transmission between saidmaster wireless transceiver station and the respective slave wirelesstransceiver device without re-transmission through another device;wherein said coordinator mechanism, responsive to each instance of aperiodic transmission of a master synchronization signal received fromsaid master device using said wireless transceiver, transmits arespective master synchronization response signal to said master deviceusing said wireless transceiver, said master synchronization signalbeing transmitted via respective direct wireless transmission from saidmaster wireless transceiver station to each slave wireless transceiverdevice of said plurality of slave wireless transceiver devices withoutre-transmission through another device, said master synchronizationsignal requiring a respective master synchronization response signalfrom each of said plurality of slave wireless transceiver devices;wherein said coordinator mechanism, responsive to receiving aninstruction signal from said master device using said wirelesstransceiver, said instruction signal urging said first slave wirelesstransceiver device to send a slave synchronization signal, saidinstruction signal having been transmitted by said master device to saidfirst slave device upon detecting in said master device a failure of asecond slave device previously connected directly to said master deviceto respond to an instance of said periodically transmitted mastersynchronization signal, sends a slave synchronization signal; whereinsaid coordinator mechanism, responsive to receiving in said first slavedevice an acknowledgment signal indicating that the second slave devicehas received the slave synchronization signal, re-transmits theacknowledgment signal to the master device; and wherein said coordinatorthereafter receives, from said master device, one or more informationpackets received in the master device via an external interface andaddressed to the second slave device, and forwards each such informationpacket to the second slave device.
 12. The first slave wirelesstransceiver device of claim 11, wherein predefined wirelesscommunications protocol is an IEEE 802.15.3 PICONET protocol.
 13. Thefirst slave wireless transceiver device of claim 11, further comprisinga table which includes a list of communicable slaves to which the firstslave device is capable of forwarding communications received from themaster device.